Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/10—Clay
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/043—Alkaline-earth metal silicates, e.g. wollastonite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00034—Physico-chemical characteristics of the mixtures
  • C04B2111/00189—Compositions or ingredients of the compositions characterised by analysis-spectra, e.g. NMR
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/20—Resistance against chemical, physical or biological attack
  • C04B2111/2023—Resistance against alkali-aggregate reaction
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the present invention concerns a method for eliminating the dangerous alkali-aggregate reaction in concretes. More specifically the mineral compounds described in this invention enable the production of a rapid-set geopolymeric cement comprising portland cement and alkali activation, the said geopolymeric cement preventing the formation in these concretes of a compound which can generate a soluble alkali aluminate, responsible for the deleterious alkali-aggregate reaction.
• the accelerating properties of small quantities of alkali salts or of alkali hydroxides on the setting of ordinary hydraulic binders are well known. This particular setting or hardening acceleration of cement, is often called alkali activation.
• alkali activation is often called alkali activation.
• drawbacks have limited its applications, for example the attack and destruction of concrete due to alkali-aggregate reaction.
• the present invention provides a remedy to these failures and enables advantage to be taken of the alkali activation properties without the said drawbacks.
• alkali activation is performed with alkali salts, sodium and/or potassium carbonates, soluble alkali silicates or sodium and/or potassium hydroxides; in the resulting mineral composition, the amount of the said alkali ingredients involves an oxide molar ratio [M 2 O]/[SiO 2 ] ⁇ 0,1, equivalent to the oxide weight ratio M2O/SiO2 ⁇ 0,15; in a preferred description of the invention, M is potassium and alkali activation is carried out with potassium carbonate. Any worker in the field knows about the rapid-set accelerating properties of potassium carbonate and the necessity of adding citric acid or potassium citrate in order to prevent any flash-set of cement.
• MAS-NMR Nuclear Magnetic Resonance spectroscopy
• MAS-NMR spectrography for 27 Al for products yielded by a geopolymeric reaction show a single peak at 55 ⁇ 5 ppm, characteristic of Al(IV) coordination and a tetrahedron (AlO 4 ) of the Q 4 (4Si) type, whereas the hydration products obtained with traditional hydraulic binders show a peak at 0 ppm, characteristic of Al(VI) coordination, i.e. of the hydroxy-aluminate of calcium.
• the portland cement based geopolymeric mineral compositions yielding a rapid-set geopolymeric cement after alkali activation [M 2 O]/[SiO 2 ] ⁇ 0,1 comprise essentially three reactive constituents:
• the inorganic compositions of the invention are also called inorganic geopolymeric compositions, since the geopolymeric cement obtained has resulted from an inorganic polycondensation reaction, a so-called geopolymerisation, unlike traditional hydraulic binders in which hardening is the result of the hydration of aluminates of calcium and silicates of calcium.
• the molar ratio [M 2 O]/[SiO 2 ] is greater than 0.1, generally ranging between 0.20 and 0.50, such as in the patents U.S. Pat. No. 4,472,199, U.S. Pat. No. 4,640,715, U.S. Pat. No. 4,642,137. They are not related to the present invention. In others, for instance U.S. Pat. No. 4,306,912, U.S. Pat. No. 4,842,649, U.S. Pat. No.
• the alkali activation of the portland cement-based hydraulic binders is of the [M 2 O]/[SiO 2 ] ⁇ 0,1-type, basically carried out by adding 0-3% by weight of potassium carbonate and 0-3% by weight of citric acid (or potassium citrate).
• the chemical compound which is related to the alkali activation of portland cement, shows a 27 Al MAS-NMR resonance at 64-66 ppm corresponding to a (Q 3 )(3Si)-type (AlO 4 ) tetrahedron, characteristic for a hydrated alkali alumino-silicate with a non tri-dimensional structure.
• the intensity of the 27 Al MAS-NMR resonance at 64-66 ppm increases with the amount of alkali available in the mix. This compound generates the production of soluble alkali aluminates which cause the deleterious alkali-aggregate reaction.
• the method disclosed in this invention does not produce any free alkali aluminates, but yields the synthesis of a tri-dimensional geopolymeric compound whose 27 Al MAS-NMR spectrum shows a main resonance at 55 ⁇ 5 ppm in relation to AlCl 3 which corresponds to a (Q 4 ) (4Si)-type (AlO 4 ) tetrahedron and is basically different from the compound obtained during the alkali activation of portland cement.
• Alumino-silicate whose MAS-NMR for 27 Al has at least one main resonance at 20 ⁇ 5ppm and/or 50 ⁇ 5ppm belong basically to the class of those having a lamellar mineralogical structure.
• alumino-silicate oxide ⁇ 9[Si 2 O 5 ,Al 2 O 2 ],[Si 2 O 5 ,Al 2 (OH) 4 ] ⁇ which is produced by calcination of a kaolinitic material, or a glass containing an alumino-silicate oxide 2CaO.Al 2 O 3 .SiO 2 , belonging to the mineralogical family of gehlinite, produced by vitrifying clays.
• One of the objects of the present invention concerns a method enabling the production of a portland based rapid-set cement, whose 27 Al MAS-NMR spectrum shows a main resonance at 55 ⁇ 5 ppm corresponding to a (Q 4 )(4Si)-type (AlO 4 ) tetrahedron.
• the said rapid-set cement results from alkali activation [M 2 O]/[SiO 2 ] ⁇ 0,1 of a basic calcium alumino-silicate x(CaO).y(Al 2 O 3 ).(SiO 2 ), where "x" has a value between 2 and 3.5 and "y” has a value between 0 and 0.2.
• the quantities of alkali added to initiate alkali activation are too low to transform all the calcium aluminate available in portland cement, into an alkali alumino-silicate, whose 27 Al MAS-NMR spectrum shows a main resonance at 55 ⁇ 5 ppm, corresponding to a (Q 4 )(4Si)-type (AlO 4 ) tetrahedron.
• the calcium alumino-silicate part in excess, not activated by the alkalis, is normally transformed into aluminum hydroxide and/or hydrated calcium sulfoaluminate.
• the rapid-set geopolymeric cement of the present invention has a 27 Al MAS-NMR spectrum which shows a resonance at 55 ⁇ 5 ppm in relation to AlCl 3 corresponding to a (Q 4 )(4Si)-type (AlO 4 ) tetrahedron and also a resonance at 0 ⁇ 5 ppm in relation to AlCl 3 corresponding to the cation Al in VI-fold coordination (AlO 6 ) of aluminum hydroxide and/or hydrated calcium sulfo-aluminate (ettringite), with a ratio between the resonance intensity (Q 4 )(4Si)-type (AlO 4 ) at 55 ⁇ 5 ppm and the resonance intensity (AlO 6 ) at 0 ⁇ 5 ppm, (AlO 4 )/(AlO 6 ) equal to or between 0.1 and 1.
• the said synthetic alumino-silicate corresponds to the alumino-silicate oxide ⁇ 9[Si 2 O 5 ,Al 2 O 2 ],[Si 2 O 5 ,Al 2 (OH) 4 ] ⁇ , produced by calcining kaolinitic materials
• the said calcination must be carried out in such ways that the 27 Al MAS-NMR spectrum for the said alumino-silicate oxide displays two main resonances at 20 ⁇ 5 ppm and 50 ⁇ 5 ppm and an additional secondary resonance, with lower intensity, at 0 ⁇ 5 ppm in relation to AlCl 3 .
• calcination parameters do determine the efficiency of the alumino-silicate oxide in relation to the claims of the present invention. For instance, when calcination is carried out at a temperature between 550° C. and 650° C., the main resonance of the 27 Al MAS-NMR spectrum is 0 ⁇ 5 ppm, highlighting a deficit in (IV-V)-coordinated Al. On the other hand, when calcination is carried out at a temperature higher than 900° C., the main resonance of the 27 Al MAS-NMR spectrum is also 0 ⁇ 5 ppm, highlighting accordingly a deficit in (IV-V)-coordinated Al. With higher calcination temperature (1000° C.-1100° C.) the calcined material comprises more mullite whose main resonance of the 27 Al MAS-NMR spectrum is also 0 ⁇ 5 ppm.
• Ideal calcination temperatures are between 700° C. and 800° C. However, in addition to temperature control, it is the kiln technology which determines the feasibility and production of the alumino-silicate oxide ⁇ 9[Si 2 O 5 ,Al 2 O 2 ],[Si 2 O 5 ,Al 2 (OH) 4 ] ⁇ described in the present invention.
• a rigid (vertical) kiln When calcination is carried out in a rigid (vertical) kiln, a sufficient water vapor pressure is maintained during the entire roasting process, providing the desired MAS-NMR spectrum for the roasted material.
• rapid calcination in rotary kilns currently employed in cement plants yields a deficit in (IV-V)-coordinated Al.
• metakaolin In general, industrial products which are called low-temperature calcined kaolins or high-temperature calcined kaolins, in use in the paper industry, commonly called metakaolin, do not react in the terms of the present invention, for the reasons explained hereabove. This is also the case for metakaolins manufactured in a rapid roasting rotary kiln by cement producers, which for example in the description of Heitzmann & al. patent U.S. Pat. No. 4,842,649, are characterised by the US codification ASTM C618-85 dedicated to calcined natural pozzolanic materials.
• metakaolin may replace potassium carbonate.
• potassium carbonate plays the main role in alkali activation, this does not mean that metakaolin does possess any alkali group. It is chemically neutral.
• metakaolin enhances the activity of potassium carbonate. Yet, as it is known that, in the cold, the solubility of potassium carbonate is slowed down, any use of metakaolin would, in terms of this patent and at these low temperatures, increase the solubility of potassium carbonate, in fact that of the potassium ion.
• any free exchange of potassium ions from complexes built into the reactive mix requires that the major part of the Aluminum, in metakaolin, is in the (AlO 6 )-type VI-fold coordination, with its typical resonance at the 0 ⁇ 5 ppm, and involves either a calcination temperature lower than 650° C. or calcination in a rotary kiln, during a very short time.
• fly-ashes by-products of the firing of coal
• the main element of these vitrified fly-ashes is mullite. It is known that, in mullite, aluminum is mainly in the (AlO 6 )-type VI-fold coordination with its typical resonance at the 0 ⁇ 5 ppm, and in a IV-fold coordination related to a resonance at 60 ppm, both resonances being different to those claimed in the present invention.
• the mineralogical structure of mullite does not belong to the group of lamellar silicates.
• fly-ashes are generally employed in the prior art, for example in the patent of Forss. According to US designation, these fly-ashes are defined as Class F, and according to ISO codification as low CaO fly-ashes. However, the patent of Heitzmann recommends the use of Class C, or high CaO, fly-ashes.
• alumino-silicate which belongs to the class of silicates with a lamellar mineralogical structure, whose mineralogical structure is lamellar and whose MAS-NMR spectrum for 27 Al has at least one main resonance at 20 ⁇ 5 ppm and/or 50 ⁇ 5 ppm in relation to AlCl 3 ; this is the calcium alumino-silicate gehlinite, 2CaO.Al 2 O 3 .SiO 2 .
• the production of calcium alumino-silicate gehlinite results essentially from the vitrification of clay material, and is carried out in such a way that, in the obtained glass, the said calcium alumino-silicate shows a MAS-NMR spectrum for 27 Al with one main resonance at 45 ⁇ 7 ppm in relation to AlCl 3 .
• Calcium disilicate Ca(H 3 SiO 4 ) 2
• Ca(H 3 SiO 4 ) 2 can be manufactured separately, for example by hydrothermal reaction between lime and silica.
• the starting material is a basic calcium silicate, i.e. with a Ca/Si atomic ratio equal to or greater than 1.
• Basic silicates such as wollastonite, Ca(SiO 3 ), gehlenite, (2CaO.Al 2 O 3 .SiO 2 ), akermanite, (2CaO.MgO.2SiO 2 ) are well suited.
• this calcium disilicate Ca(H 3 SiO 4 ) 2 reacts with the alkali aluminate generated by the basic calcium alumino-silicate x(CaO).y(Al 2 O 3 ).(SiO 2 ), with the formation of geopolymeric bonds of the poly(sialate-siloxo)-type (--Si--O--Al--O--Si--O--), and the production of a geopolymeric tridimensional framework where the 27 Al MAS-NMR spectrum shows a main resonance at 55 ⁇ 5 ppm in relation to AlCl 3 which corresponds to a (Q 4 )(4Si)-type (AlO 4 ) tetrahedron.
• blast-furnace slag As the papers SP114-16 (American Concrete Institute) outlined hereabove, when the amount of blast-furnace slag to portland cement is less than 40-45% by weight, there is an increase in the danger with respect to the alkali-aggregate reaction.
• the quantities of these industrial by-products are lower than 30% by weight of portland cement, there is elimination of the dangerous alkali-aggregate reaction.
• bottom-ashes obtained by firing coals at a very high temperature, with a firing temperature being high enough to completely vitrify the ashes, do not contain any free lime CaO.
• these industrial by-products are essentially selected by comparing their 27 Al MAS-NMR spectra which must display at least one main resonance at 20 ⁇ 5 ppm and/or 50 ⁇ 5 ppm in relation to AlCl 3 .
• formulations disclosed within the terms of the present invention may also comprise any additives and fillers commonly in usage with regular hydraulic binders.
• the basic calcium alumino-silicate x(CaO).y(Al 2 O 3 ).(SiO 2 ) is a portland cement which has the following analysis:
• the cement has the following Nuclear Magnetic Resonance spectra:
• a powder blend is prepared consisting of:
• a standard sand mortar is prepared employing this blend, with a cement/water ratio equal to 0.28. This mortar sets after 30 minutes and has a compressive strength of 21 MPa after 4 hours and 40 MPa after 24 hours, at room temperature.
• the hardened mortar has the following Nuclear Magnetic Resonance spectra:
• a blend is prepared consisting of
• the synthetic alumino-silicate ⁇ 9[Si 2 O 5 ,Al 2 O 2 ],[Si 2 O 5 ,Al 2 (OH) 4 ] ⁇ is prepared by calcining kaolinitic material in a rigid (vertical) kiln at 750° C. during 5 hours, to provide an oxide alumino-silicate whose 27 Al MAS-NMR spectrum shows resonance intensities at 22 ppm and 50 ppm which are 40% higher than the intensity of the secondary resonance at 0 ppm, in relation to AlCl 3 .
• the basic blast-furnace slag contains at least 70% of mellilitic glass, an eutecticum comprising gehlinite and ackermanite. Its 27 Al MAS-NMR spectrum shows a broad band with a peak at 47 ppm.
• a mortar, as in Example 1, is prepared employing the blend of this Example 2. This mortar sets after 30 minutes and has a compressive strength of 19 MPa after 4 hours and 37 MPa after 24 hours, at room temperature.
• the hardened mortar has the following Nuclear Magnetic Resonance spectra:
• Example 1 To the powder blend of Example 1 is added 18 parts of vitrified ashes with the following analysis:
• This powder blend has the following Nuclear Magnetic Resonance spectra:
• a mortar, as in Example 1, is prepared employing the blend of this Example 3. This mortar sets after 45 minutes and has a compressive strength of 20 MPa after 4 hours and 42 MPa after 24 hours, at room temperature.
• the hardened mortar has the following Nuclear Magnetic Resonance spectra:

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• Ceramic Engineering (AREA)
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• Organic Chemistry (AREA)
• Civil Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 1990
  • 1990-02-05 FR FR9001278A patent/FR2657867B1/fr not_active Expired - Fee Related
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